Strictus

Strict Typing for local variables in PHP

Introduction | Installation | Usage | Credits | Contributing

Introduction

Strictus brings strict typing for local variables into PHP.

With Strictus, you can control the types of local variables using different patterns.

💣 The problem:

PHP has no support for strongly typed Local Variables.

Here is an illustrative example of a basic mistake:

<?php 
//Rule: Active discount of 10% or 25% for orders from $50

$total = 82.50;
$discount = 0.10; //float

if ($total >= 50) {
    $discount = '25%'; //replacing a float value with string value 🤦🏻‍♂️
}

$total = $total - ($total * $discount); //💥 Error: A float cannot be multiplied by a string

In the code above, nothing prevents overriding the float value of $discount a string value, causing a bug.

👍 The solution:

Let's rewrite the previous example using Strictus and strongly typed variables:

<?php 
//Rule: Active discount of 10% or 25% for orders from $50

use Strictus\Strictus;

$total = Strictus::float(82.50); 
$discount = Strictus::float(0.10);

if ($total() >= 50) {
    $discount(0.25); //updates the $discount value
}

$total($total() - ($total() * $discount()));

echo $total(); //61.875

In the code above, the variable $discount is an instance of StrictusFloat::class and it only accepts float values.

An Exception StrictusTypeException is thrown when we try to assign anything that is not of type float, like a string for example.

See this example:

<?php 
use Strictus\Strictus;

$discount = Strictus::float(0.10);
$discount('25%'); //A StrictusTypeException stops the code execution

Installation

You can install the package via composer:

composer require strictus/strictus

Requires: PHP 8.1+

Usage

There are a few different patterns you can use to work Strictus.

Creating Your Variables

To create a variable, simply call Strictus::*method*(), replacing the *method* with the type you want to enforce.

For example:

<?php
use Strictus\Strictus;

//creates a string
$name = Strictus::string('Wendell');

 //creates a nullable string
$comment = Strictus::nullableString(null);

 //creates an int
$score = Strictus::int(100);

//creates a boolean
$isActive = Strictus::boolean(true);

//creates an array
$authors = Strictus::array(['Wendell', 'Christopher']);

//creates an object
$person = Strictus::object((object) ['name' => 'Wendell', 'country' => 'BR']);

//instantiates a class
$calculator = Strictus::instance(CalculatorClass::class, new CalculatorClass());

//instantiates an enum
$role = Strictus::enum(Role::class, Role::CONTRIBUTOR);

class CalculatorClass
{
    //...
}

enum Role
{
    case CONTRIBUTOR;
}

💡 Check out all the available variable methods.

Getting Variable Value

To retrieve the variable value, just call it like a function:

echo $name(); //Wendell

echo $score() - 10; //90

if ($isActive()) {
    //do your logic here
}

echo implode($authors(), ';'); //Wendell;Christopher

Alternatively, you can use the $variable like a Value Object:

$name = Strictus::string('Christopher'); //creates a string

echo $name->value; //Christopher

Update Variable Value

To update the variable value, call it like a function passing the new value as the argument:

$score = Strictus::int(100);

$score($score() - 20); //updates $score

echo $score(); //80

Alternatively, you can use the $variable like a Value Object:

$score = Strictus::int(100);

$score->value = 0;

echo $score(); //0

Variable methods

You can use the following methods to create single type variables:

Type	Nullable	Method
String	No	Strictus::string($value)
String	Yes	Strictus::string($value, true)
String	Yes	Strictus::nullableString($value)
Integer	No	Strictus::int($value)
Integer	Yes	Strictus::int($value, true)
Integer	Yes	Strictus::nullableInt($value)
Float	No	Strictus::float($value)
Float	Yes	Strictus::float($value, true)
Float	Yes	Strictus::nullableFloat($value, true)
Boolean	No	Strictus::boolean($value)
Boolean	Yes	Strictus::boolean($value, true)
Boolean	Yes	Strictus::nullableBoolean($value)
Array	No	Strictus::array($value)
Array	Yes	Strictus::array($value, true)
Array	Yes	Strictus::nullableArray($value)
Object	No	Strictus::object($value)
Object	Yes	Strictus::object($value, true)
Object	Yes	Strictus::nullableObject($value)
Class Type	No	Strictus::instance($instanceType, $value)
Class Type	Yes	Strictus::instance($instanceType, $value, true)
Class Type	Yes	Strictus::nullableInstance($instanceType, $value)
Enum Type	No	Strictus::enum($enumType, $value)
Enum Type	Yes	Strictus::enum($enumType, $value, true)
Enum Type	Yes	Strictus::nullableEnum($enumType, $value)

Union Types

Strictus also supports union types:

use Strictus\Enums\Type;

$unionTypesVariable = Strictus::union([Type::INT, Type::STRING], 'foo');

echo $unionTypesVariable->value; //foo

echo $unionTypesVariable(); //foo

// Update variable

$unionTypesVariable->value = 100;

echo $unionTypesVariable->value; //100

// Thrown an exception if the value is wrong union types

$unionTypesVariable->value = false; //StrictusTypeException

Immutable Variables

If you want to create immutable variables, you can use the ->immutable() method. If you try to assign a new value to an Immutable Variable, an Strictus\Exceptions\ImmutableStrictusException exception will be thrown:

$immutableScore = Strictus::int(100)->immutable();

$immutableScore(50); //ImmutableStrictusException
$immutableScore->value = 50; //ImmutableStrictusException

Error Handling

If you try to assign a value that doesn't match the type of the created variable, an Strictus\Exceptions\StrictusTypeException exception will be thrown:

$score = Strictus::int(100);

$score('one hundred'); //StrictusTypeException
$score->value = false; //StrictusTypeException

If you try to assign a new value to an Immutable Variable, an Strictus\Exceptions\ImmutableStrictusException exception will be thrown:

$immutableScore = Strictus::int(100)->immutable();

$immutableScore(50); //ImmutableStrictusException
$immutableScore->value = 50; //ImmutableStrictusException

Motivation

Following a discussion on Twitter between Christopher Miller and Wendell Adriel around the lack of strongly typed local variables for PHP we quickly decided a package was the right approach whilst we could get an RFC into the core.

Credits

Contributing

We welcome contributions!

Please visit the Contributing Guide to learn more about contributing to Strictus.

php-strictus/strictus